Looking to buy a ductless heat pump system (condensers outside, wall units inside). Also seen them called "mini splits". Single level house of 1500sf, southern New England. Mainly looking for the A/C, but I'm told the heating is somewhat efficient down to about freezing. The questions begin: What brands are considered the most efficient and least problematic? Are there any efficient systems that will heat below freezing? What SEER should I be looking for? Are more efficient units worth the extra money, i.e., how long to amortize extra costs? What should I be looking for in a good installation? What would indicate a bad installation? Any additional info experts in the field could contribute would be greatly appreciated!